This invention relates to a video and audio data processing method and apparatus by which digital data representative of a video signal and digital data representative of an audio signal are processed so as to have a format for transmission thereof through a data transmission line such as a coaxial cable.
In order to allow transmission of digital video data (DV data) and digital audio data (DA data) obtained by digitizing a video signal and an audio signal which make signal elements which form a television broadcasting signal and representative of the video signal and the audio signal, respectively, through a data transmission line formed from, for example, a coaxial cable, the DV data and the DA data are normally processed so that they may have a format set in advance. Various formats are available for the format, and a format called serial data interface (SDI) format has been proposed as one of such formats.
In order to transmit DV data and DA data using the SDI format, the DV data and the DA data to be transmitted are divided into and placed as a series of successive data segments DP each of which corresponds to a one line period (1 H) beginning with a horizontal synchronizing signal SSH of a video signal SV. Each data segment DP includes an EAV part of a 4 word-structure, an ancillary area part of a 268 word-structure, an SAV part of a 4 word-structure and a payload area part of a 1,440 word-structure and is totally composed of 1,716 words.
In each data segment DP, DV data are placed for 1,440 words in the maximum in the payload area part, and DA data are placed for 268 words in the maximum in the ancillary area part. Where the DV data and the DA data to be transmitted are a video signal and an audio signal which form a television signal conforming to the NTSC system, DV data for a one frame period of the video signal (for the first and second field periods) and corresponding DA data are placed in 525 successive data segments DP.
FIG. 2 illustrates an example of a condition wherein DV data for a one frame period of a video signal and corresponding DA data are placed in 525 successive data segments DP. It is to be noted that reference symbol NL in FIG. 2 represents the number of each data segment DP. In the example illustrated in FIG. 2, DV data for a 240 line period which is a first field period for the video signal are placed in the payload area parts of 244 data segments DP beginning with the 20th one and ending with the 263rd one of the 525 successive data segments DP, and DA data corresponding to the DV data are placed in the ancillary area parts of the 244 data segments DP beginning with the 20th data segment DP and ending with the 263rd data segment DP. Further, DV data for another 240 line period which is a second field period for the video signal are placed in the payload area parts of 243 data segments DP beginning with the 283rd one and ending with the 525th one of the 525 successive data segments DP, and DA data corresponding to the DV data are placed in the ancillary area parts of the 243 data segments beginning with the 283rd data segment DP and ending with the 525th data segment DP.
When transmission of DV data and DA data is performed using the SDI format in such a manner as described above, data segments DP in the payload area parts of which the divided DV data are placed and in the ancillary area parts of which the divided DA data are placed are successively transmitted through data transmission lines. In this instance, one set of DV data and DA data is transmitted for each one data transmission line. Accordingly, in order to transmit a plurality of sets of DV data and DA data which are different from each other substantially simultaneously or in a common transmission period, a plural number of data transmission lines equal to the number of sets of DV data and DA data are required even if the data are to be transmitted to a common transmission destination.
For example, in order to transmit 10 sets of DV data and DA data substantially simultaneously or in a common transmission period to a common transmission destination, 10 data transmission lines are required, and if it is assumed that each of the data transmission lines is formed by a coaxial cable, then it is required to lay 10 coaxial cables. To provide a plurality of data transmission lines each formed from, for example, a coaxial cable in this manner gives rise to complication and increase in scale of an apparatus or equipment for data transmission and further to an increase in cost for data transmission.
It is an object of the present invention to provide a video and audio data processing method and apparatus by which, when a plurality of sets of DV data and DA data are to be processed so as to have a data format such as the SDI format which allows them to be transmitted substantially simultaneously or in a common transmission period to a common transmission destination, the necessity for provision of a number of data transmission lines equal to the number of sets of DV data and DA data in order to allow transmission of the plurality of sets of DV data and DA data can be eliminated to eliminate complication and increase in scale of an apparatus or equipment for data transmission and decrease the cost for data transmission.
In order to attain the object described above, according to an aspect of the present invention, there is provided a video data processing method, comprising the steps of performing compressed video data selective extraction wherein data compression is performed for a plurality of digital video data individually representative of a plurality of video signals to obtain a plurality of compressed video data and a predetermined number of words are successively and repetitively extracted from each of the plurality of compressed video data and audio data selective extraction wherein a predetermined number of words are successively and repetitively extracted from a plurality of digital audio data individually representative of a plurality of audio signals, successively forming data segments each having a first data area in which the predetermined number of words of each of the plurality of digital audio data extracted by the audio data selective extraction are placed and a second data area in which the predetermined number of words of each of the plurality of compressed video data extracted by the video data selective extraction are placed such that the plurality of compressed video data individually representative of the plurality of video signals for a predetermined period are placed divisionally with the predetermined numbers of words in the second data areas of a predetermined number of the successive data segments, and successively sending out the predetermined numbers of data segments.
Preferably, each of the data segments corresponds to a one line period of a video signal, and the plurality of compressed video data representative of the plurality of video signals for the one frame period are placed divisionally with the predetermined number of words in the second data areas of a number of the successive data segments equal to the number of line periods which form the one frame period of the video signal.
According to another aspect of the present invention, there is provided a video data processing apparatus, comprising a plurality of data compression sections for performing data compression individually for a plurality of digital video data individually representative of a plurality of video signals to obtain a plurality of compressed video data, a plurality of first memory sections for storing the plurality of compressed video data obtained by the plurality of data compression sections and successively and repetitively reading out the plurality of compressed video data for each predetermined number of words, a plurality of second memory sections for storing a plurality of digital audio data individually representative of a plurality of audio signals and successively and repetitively reading out the plurality of digital audio data for each predetermined number of words, and an encoder section for successively forming data segments each having a first data area in which the predetermined number of words of each of the plurality of digital audio data read out from the plurality of second memory sections are placed and a second data area in which the predetermined number of words of each of the plurality of compressed video data read out from the plurality of first memory sections are placed such that the plurality of compressed video data individually representative of the plurality of video signals for a predetermined period are placed divisionally with the predetermined numbers of words in the second data areas of a predetermined number of the successive data segments and successively sending out the predetermined numbers of data segments.
Preferably, the encoder section forms data segments such that each of the data segments corresponds to a one line period of a video signal, and divisionally places the plurality of compressed video data representative of the plurality of video signals for the one frame period with the predetermined number of words into the second data areas of a number of the successive data segments equal to the number of line periods which form the one frame period of the video signal.
In the video and audio data processing method and the video and audio data processing apparatus according to the present invention described above, data segments formed for transmission of video data and audio data are placed, for each predetermined number of words of each of a plurality of audio data, into a first data area and placed, for each predetermined number of words of each of a plurality of compressed video data based on a plurality of video data, into a second area. Then, a group unit of data segments is formed from a predetermined number of successive data segments wherein the predetermined numbers of words of the audio data are placed in the first data areas and the predetermined numbers of words of the compressed video data are placed in the second data areas such that the plurality of compressed video data individually representative of the plurality of video signals for a predetermined period are placed divisionally with the predetermined numbers of words in the second data areas of a predetermined number of the successive data segments included in each of the group units. In this instance, in the first data areas of the predetermined number of data segments included in each of the group units, the plurality of audio data corresponding to the plurality of compressed video data of the plurality of video signals for the predetermined period are divisionally placed with the predetermined numbers of words.
Where each of the data segments corresponds to a one line period of a video signal, the number of data segments included in each of the group units corresponds to the number of line periods which form a one frame period of the video signal, and in the predetermined number of data segments, the plurality of compressed video data corresponding to the one frame periods of the plurality of video signals are divisionally placed with the predetermined numbers of words in the second data areas while the plurality of audio data corresponding to the one frame periods of the video signals are divisionally placed with the predetermined numbers of words in the first data areas.
Consequently, a plurality of sets of compressed video data and audio data are successively placed, for each data amount corresponding to a one frame period of a video signal, into group units each of which is formed from a predetermined number of successive data segments. Then, the group units of the data segments formed successively in this manner can be successively transmitted through a single transmission line formed from a coaxial cable. Accordingly, a condition wherein a plurality of sets of compressed video data and audio data can be transmitted substantially simultaneously or in a common transmission period to a common transmission destination.
Therefore, where the video and audio data processing method or the video and audio data processing apparatus according to the present invention is applied to perform processing for formation of a large number of successive data segments so that a plurality of sets of video data and audio data may have a data format such as the SDI format with which they can be transmitted substantially simultaneously or in a common transmission period to a common transmission destination, in order to transmit a plurality of sets of video data and audio data, there is no need of providing a plural number of data transmission lines equal to the number of sets of video data and audio data. Therefore, such a situation that complication and increase in scale of an apparatus or equipment for data transmission are invited can be eliminated, and further, reduction in cost for data transmission can be achieved.
The above and other objects, features and advantages of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings in which like parts or elements are denoted by like reference characters.